Chapter 15Chapter 15

The Brain and Cranial NervesThe Brain and Cranial Nerves

The BrainThe Brain The average male adult brain weighs The average male adult brain weighs

about 3.5 lbs. about 3.5 lbs. Composed of 3 divisions:Composed of 3 divisions:

CerebrumCerebrum = Cerebral cortex and Basal = Cerebral cortex and Basal nucleinuclei

CerebellumCerebellum – posterior and inferior to – posterior and inferior to cerebrumcerebrum

Brainstem: Diencephalon (Thalamus, Brainstem: Diencephalon (Thalamus, Hypothalamus and Epithalamus), Midbrain Hypothalamus and Epithalamus), Midbrain (superior and inferior colliculi), Pons and (superior and inferior colliculi), Pons and Medulla oblongataMedulla oblongata

Brain MeningesBrain Meninges

Arachnoid villiArachnoid villi

Absorbs CSF back into venous sinuses Absorbs CSF back into venous sinuses and bloodand blood

Brain VentriclesBrain Ventricles Cavities within the cerebrum and brain stem where Cavities within the cerebrum and brain stem where

cerebrospinal fluid (CSF) is manufactured and circulated.cerebrospinal fluid (CSF) is manufactured and circulated.

Two lateral ventricles over thalamus and roll out into temporal Two lateral ventricles over thalamus and roll out into temporal lobes, medial third and fourth ventricles joined by cerebral lobes, medial third and fourth ventricles joined by cerebral aqueduct.aqueduct.

Lateral ventricles look like a Rocky Mountain sheep Rams Lateral ventricles look like a Rocky Mountain sheep Rams horns and communicate to third ventricle via interventricular horns and communicate to third ventricle via interventricular foreamen.foreamen.

CSF is formed by the ependymal cells of choroid plexus in all CSF is formed by the ependymal cells of choroid plexus in all

four ventricles; is an ultrafiltrate of blood- no cells present; four ventricles; is an ultrafiltrate of blood- no cells present; high in Na and K.high in Na and K.

CSF circulates through ventricular system as well as central CSF circulates through ventricular system as well as central canal of spinal cord and subarachnoid space around brain and canal of spinal cord and subarachnoid space around brain and spinal cord.spinal cord.

Brain VentriclesBrain Ventricles

CSF formation and CSF formation and circulation into and circulation into and from blood vascular from blood vascular systemsystem..

CSF provides CSF provides protection and protection and nourishment to the nourishment to the brain and spinal brain and spinal cord.cord.

Has higher levels of Has higher levels of Na and K than blood.Na and K than blood.

CSF reduces weight CSF reduces weight of brain (1400 gm to of brain (1400 gm to 50 gm).50 gm).

CerebrumCerebrum Cerebrum composes the vast majority of the Cerebrum composes the vast majority of the

brain mass (80%). It is divided into 2 halves brain mass (80%). It is divided into 2 halves or or hemisphereshemispheres, a right and a left hemisphere, a right and a left hemisphere..

Longitudinal fissure- Longitudinal fissure- midsagittal groove midsagittal groove dividing the two hemispheres into a right and dividing the two hemispheres into a right and left side.left side.

Consists of an outer layer of gray matter over Consists of an outer layer of gray matter over white matter (like crust on white bread).white matter (like crust on white bread).

Sulci and gyri = valleys and ridges on surface Sulci and gyri = valleys and ridges on surface of cerebral hemispheres.of cerebral hemispheres.

Five lobes: Frontal, parietal, occipital, Five lobes: Frontal, parietal, occipital, temporal and insula.temporal and insula.

Brain blood flow and Brain blood flow and barrierbarrier

Blood flow to the brain is provided by the Blood flow to the brain is provided by the internal carotid arteries and the vertebral internal carotid arteries and the vertebral arteries.arteries.

The blood brain barrier (BBB) is thought to The blood brain barrier (BBB) is thought to be due to specialized endothelial cells that be due to specialized endothelial cells that are influenced by the glial astrocytes.are influenced by the glial astrocytes.

In the choroid plexus there is also a CSF-BBB In the choroid plexus there is also a CSF-BBB formed by the ependymal cells.formed by the ependymal cells.

The BBB is absent in some places of the 3The BBB is absent in some places of the 3rdrd and 4and 4thth ventricles at patches called ventricles at patches called circumventricular organs where some circumventricular organs where some substances may pass into the brain tissue.substances may pass into the brain tissue.

Cerebral CortexCerebral Cortex

The cortex is the outer layer of the The cortex is the outer layer of the cerebrum is composed of cerebrum is composed of gray mattergray matter and is where our “consciousness” is and is where our “consciousness” is located. located.

It allows us to be who we are, perceive It allows us to be who we are, perceive sensations, comprehend and understand, sensations, comprehend and understand, as well as learn and, communicate with as well as learn and, communicate with the ability to act and react at a conscious the ability to act and react at a conscious level. level.

Sulcus or SulciSulcus or Sulci

sulcus/sulci –sulcus/sulci – the valleys or grooves the valleys or grooves found between the gyri. Some of these found between the gyri. Some of these also have specific names.also have specific names. central sulcuscentral sulcus – separates the – separates the

frontal and parietal lobes..frontal and parietal lobes.. lateral sulcuslateral sulcus – separates the – separates the

temporal lobe from the parietal/ temporal lobe from the parietal/ frontal lobes.frontal lobes.

parietoparieto--occipital sulcusoccipital sulcus – – separates separates the parietal and occipital lobes.the parietal and occipital lobes.

Gyrus or GyriGyrus or Gyri

gyrus/gyri – gyrus/gyri – the elevated ridges of tissue in the elevated ridges of tissue in the cortexthe cortex

1. precentral gyrus- 1. precentral gyrus- motor cortex area 4motor cortex area 4 2. post central gyrus- 2. post central gyrus- sensory cortex sensory cortex

areas 1-3areas 1-3 - homunculus (little man)- - homunculus (little man)-

portrays motor and sensory areas of body portrays motor and sensory areas of body overlaying precentral and postcentral gyri overlaying precentral and postcentral gyri of the cortexof the cortex

Sulci and GyriSulci and Gyri

Humunculus “little man”Humunculus “little man”

Functional areas of the Functional areas of the CortexCortex

Three important areas of Three important areas of cortexcortex

Motor areasMotor areas control voluntary control voluntary movement.movement.

Sensory areasSensory areas provide consciousness and provide consciousness and awareness of sensations.awareness of sensations.

Association areasAssociation areas act mainly to integrate act mainly to integrate diverse information into decisive and diverse information into decisive and meaningful actions. This is done via meaningful actions. This is done via interneurons or association neurons.interneurons or association neurons.

Cortical motor, sensory and Cortical motor, sensory and association areasassociation areas

Motor Areas of Cerebral Motor Areas of Cerebral CortexCortex

1° (primary) Motor Cortex1° (primary) Motor Cortex – – located in the located in the precentral gyrusprecentral gyrus.. Also known as Broadmann’s Also known as Broadmann’s area # 4.area # 4.

-Contains large Pyramidal neurons that allow us -Contains large Pyramidal neurons that allow us to perform precise and skilled movements with to perform precise and skilled movements with our skeletal muscles. our skeletal muscles.

-Motor innervation is contralateral i.e. the left -Motor innervation is contralateral i.e. the left side of the brain controls the right side of the side of the brain controls the right side of the body and vice versa.body and vice versa.

Broca’s AreaBroca’s Area – – located superior to lateral sulcus and located superior to lateral sulcus and anterior to precentral gyrus.anterior to precentral gyrus. Associated with motor Associated with motor speech and is usually located in speech and is usually located in the left hemisphere the left hemisphere

Premotor cortexPremotor cortex anterior to precentral gyrus anterior to precentral gyrus (Broadmann 6). (Broadmann 6).

thought to be site of memory bank for fine motor skils. thought to be site of memory bank for fine motor skils.

Sensory Areas of Sensory Areas of Cerebral CortexCerebral Cortex

1° (primary) Somatosensory Cortex1° (primary) Somatosensory Cortex – – located in the located in the postcentral gyrus postcentral gyrus of the of the parietal lobe. Areas 1-3parietal lobe. Areas 1-3

Visual Sensory AreaVisual Sensory Area – – Located on the Located on the extreme posterior tip of the occipital lobe.extreme posterior tip of the occipital lobe.

Receives input from retina; is largest Receives input from retina; is largest cortical sensory area. cortical sensory area.

Auditory AreaAuditory Area – – medial aspects of the medial aspects of the temporal lobes. temporal lobes.

Gustatory AreaGustatory Area – –parietal lobe deep to the parietal lobe deep to the temporal lobe at the tip of the tongue of temporal lobe at the tip of the tongue of humunculus.humunculus.

Cerebral anatomy to Cerebral anatomy to knowknow

Longitudinal and transverse fissuresLongitudinal and transverse fissures Lateral, Central and Parieto-occipital Lateral, Central and Parieto-occipital

sulcisulci Precentral (motor #4) and Postcentral Precentral (motor #4) and Postcentral

(sensory #1-3) gyri(sensory #1-3) gyri Lobes: Frontal, Parietal, Temporal, Lobes: Frontal, Parietal, Temporal,

Occipital and InsulaOccipital and Insula Basal nuclei: Caudate nucleus, Putamen, Basal nuclei: Caudate nucleus, Putamen,

Globus pallidusGlobus pallidus Corpus callosum, septum pellucidum, Corpus callosum, septum pellucidum,

fornix, and internal capsulefornix, and internal capsule

Cerebral anatomy to Cerebral anatomy to knowknow

White matter is myelinated neuronal White matter is myelinated neuronal tissue in brain and spinal cord and tissue in brain and spinal cord and contains neuronal tracts.contains neuronal tracts.

Gray matter is unmyelinated and Gray matter is unmyelinated and contains mostly neuronal nuclear groups contains mostly neuronal nuclear groups or nuclei and unmyelinated tracts.or nuclei and unmyelinated tracts.

Coronal sectionCoronal section

Cerebral White MatterCerebral White Matter is composed of is composed of myelinated processesmyelinated processes. Within the . Within the

white matter are “roads” of ordered groups of white matter are “roads” of ordered groups of neuron processes called neuron processes called tractstracts. . There are three There are three major types of tracts in the cerebral cortex:major types of tracts in the cerebral cortex:

1.1. Commissural fibersCommissural fibers – – connect the gray matter connect the gray matter between the two hemispheres. e.g. corpus between the two hemispheres. e.g. corpus callosumcallosum

2.2. Association fibersAssociation fibers – – connect adjacent gyri in connect adjacent gyri in same hemisphere. e.g. visual and auditory same hemisphere. e.g. visual and auditory association areas.association areas.

3.3. Projection fibersProjection fibers – – these connect to regions these connect to regions outside of the cerebrum e.g. internal capsule; outside of the cerebrum e.g. internal capsule; corona radiatacorona radiata

Communication fibersCommunication fibers

Communication fibersCommunication fibers

Basal Nuclei “Corpus Basal Nuclei “Corpus striatum”striatum”

Masses of cerebral gray matter buried deep Masses of cerebral gray matter buried deep in each hemisphere in the white matter and in each hemisphere in the white matter and lateral to the thalamus.lateral to the thalamus.

Caudate nucleus, globus pallidus and Caudate nucleus, globus pallidus and putamenputamen Communicate with cortex in controlling movementCommunicate with cortex in controlling movement Complete function is ??, but may regulate start, Complete function is ??, but may regulate start,

stop and intensity of voluntary body movements stop and intensity of voluntary body movements from cortical levels.from cortical levels.

Basal Nuclei “Corpus Basal Nuclei “Corpus striatum”striatum”

The Limbic SystemThe Limbic System Concerned with sense of smell in Concerned with sense of smell in

association with long term memory and association with long term memory and emotional responses (anger, fear, rage, emotional responses (anger, fear, rage, sex and hunger).sex and hunger).

Includes cingulate gyrus, amygdala, Includes cingulate gyrus, amygdala, hippocampus, septum, fornix, thalamus, hippocampus, septum, fornix, thalamus, hypothalamus and olfactory bulbs.hypothalamus and olfactory bulbs.

The Limbic SystemThe Limbic System

DiencephalonDiencephalon ThalamusThalamus is sensory relay nucleus from spinal cord is sensory relay nucleus from spinal cord

and brainstem regions to the cerebral cortex. and brainstem regions to the cerebral cortex. Located at top of brainstem, each half is joined by Located at top of brainstem, each half is joined by intermediate mass.intermediate mass.

HypothalamusHypothalamus nuclear group just inferior to nuclear group just inferior to thalamus consisting of ~ 12 nuclei. Third ventricle thalamus consisting of ~ 12 nuclei. Third ventricle is roof. is roof.

-Main visceral control center for many systems: -Main visceral control center for many systems: regulates ANS, GI, cardiovascular centers, regulates ANS, GI, cardiovascular centers, sleep/wake, emotions, behavior, hunger/thirst, body sleep/wake, emotions, behavior, hunger/thirst, body temp, memory, sex drive and endocrine system.temp, memory, sex drive and endocrine system.

EpithalamusEpithalamus pineal gland and habenula produce pineal gland and habenula produce melatonin for sleep/wake.melatonin for sleep/wake.

Diencephalon, Midbrain, Pons and Diencephalon, Midbrain, Pons and MedullaMedulla

HypothalamusHypothalamus

EpithalamEpithalamusus-Pineal gland-Pineal gland

-Habenular nuc. -Habenular nuc.

Cerebral and Diencephalon Cerebral and Diencephalon FunctionsFunctions

Brain stemBrain stem (see Figure 15.7; p. 422) (see Figure 15.7; p. 422)

Extends from posterior border of diencephalon Extends from posterior border of diencephalon to the beginning of spinal cord at foreamen to the beginning of spinal cord at foreamen magnum.magnum.

Consists of Midbrain, Pons, and Medulla Consists of Midbrain, Pons, and Medulla oblongataoblongata-controls automatic behavior of systems necessary for -controls automatic behavior of systems necessary for

life (e.g. cardiovascular, respiratory, emetic, etc.)life (e.g. cardiovascular, respiratory, emetic, etc.)-passageway for all tracts to cerebrum and spinal cord-passageway for all tracts to cerebrum and spinal cord-contains nuclei of many cranial nerves to face and -contains nuclei of many cranial nerves to face and

neckneck Has same pattern of gray/white matter as spinal cord Has same pattern of gray/white matter as spinal cord

(i.e. white matter surrounds gray matter)(i.e. white matter surrounds gray matter)

Brain Stem Brain Stem (Lateral view)(Lateral view)

Brain StemBrain Stem (Diencephalon, Midbrain (Diencephalon, Midbrain and Hindbrain)and Hindbrain)

MidbrainMidbrain Lies between a plane that extends from behind Lies between a plane that extends from behind

pineal gland down to posterior end of mamillary pineal gland down to posterior end of mamillary bodies and caudally to the rostral part of the pons.bodies and caudally to the rostral part of the pons.

Central cavity is cerebral aqueduct with tectum Central cavity is cerebral aqueduct with tectum (roof) dorsally and cerebral peduncles ventrally.(roof) dorsally and cerebral peduncles ventrally.

Periaqueductal gray is involved in fight or flight Periaqueductal gray is involved in fight or flight (Sympathetic)(Sympathetic)

Contains copra quadrigemina (sup & inf colliculi) Contains copra quadrigemina (sup & inf colliculi) which are relay nuclei for vision and hearing, which are relay nuclei for vision and hearing, respectively.respectively.

Other nuclei include substantia nigra and red Other nuclei include substantia nigra and red nucleusnucleus

Contains nuclei for occulomotor (CN-III) and Contains nuclei for occulomotor (CN-III) and trochlear (CN-IV).trochlear (CN-IV).

Midbrain/Pons Midbrain/Pons (X-section)(X-section)

Midbrain/Hindbrain Midbrain/Hindbrain (lateral (lateral view)view)

Reticular FormationReticular Formation Composed of 100’s of small gray nuclei that Composed of 100’s of small gray nuclei that

extend from medulla, pons and midbrain and extend from medulla, pons and midbrain and project up to the diencephalon, cerebellum and project up to the diencephalon, cerebellum and cerebrum.cerebrum.

It receives diverse input and sends a continuous It receives diverse input and sends a continuous stream of information to cerebral cortex stream of information to cerebral cortex keeping it alert to all activity during sleep and keeping it alert to all activity during sleep and consciousness. It is often referred to as the consciousness. It is often referred to as the reticular activating systemreticular activating system (RAS).(RAS).

The motor portion sends neurons to the spinal The motor portion sends neurons to the spinal cord via reticulospinal tracts.cord via reticulospinal tracts.

Functions include cardiovascular control, pain Functions include cardiovascular control, pain control,control,

breathing, swallowing, and habituation to breathing, swallowing, and habituation to environment.environment.

Reticular FormationReticular Formation

PonsPons Bulging region on inferior surface of brain Bulging region on inferior surface of brain

stem.stem. Lies between the midbrain and medulla Lies between the midbrain and medulla

oblongata.oblongata. Forms a bridge between left and right halves Forms a bridge between left and right halves

of cerebellum.of cerebellum. Fourth ventricle separates pons from Fourth ventricle separates pons from

cerebellum.cerebellum. Cranial nerves V (trigeminal), VI (abducens), Cranial nerves V (trigeminal), VI (abducens),

and VII (facial) arise from pontine nuclei.and VII (facial) arise from pontine nuclei. Middle cerebellar peduncles carry fibers Middle cerebellar peduncles carry fibers

from Pons to cerebellum.from Pons to cerebellum.

PonsPons

Pons Pons (lateral view)(lateral view)

Medulla oblongataMedulla oblongata Extends from Pons to spinal cordExtends from Pons to spinal cord Pyramids (pyramidal tracts) decussate Pyramids (pyramidal tracts) decussate

(crossover) at caudal border and are (crossover) at caudal border and are motor corticospinal tracts. motor corticospinal tracts.

Cranial nerves VIII (vestibulocochlear), Cranial nerves VIII (vestibulocochlear), IX (glossopharyngeal), X (Vagus), XI IX (glossopharyngeal), X (Vagus), XI (accessory) and XII (hypoglossal) arise (accessory) and XII (hypoglossal) arise from medullary nuclei near fourth from medullary nuclei near fourth ventricle.ventricle.

Visceral centers for cardiac, vasomotor Visceral centers for cardiac, vasomotor and respiratory centers are in medulla.and respiratory centers are in medulla.

Medulla oblongataMedulla oblongata

CerebellumCerebellum Cauliflower-like looking mass at posterior part Cauliflower-like looking mass at posterior part

of brain and dorsal to the pons and medulla.of brain and dorsal to the pons and medulla. Coordinates and smoothes body movements, Coordinates and smoothes body movements,

and maintains posture and equilibrium.and maintains posture and equilibrium. Two lateral hemispheres are connected by Two lateral hemispheres are connected by

vermisvermis Hemispheres subdivided into 3 lobes: Hemispheres subdivided into 3 lobes:

1. anterior, 2. posterior and 3. 1. anterior, 2. posterior and 3. flocculonodularflocculonodular

Anterior and posterior coordinate movementsAnterior and posterior coordinate movements Flocculonodular adjusts posture and Flocculonodular adjusts posture and

equilibriumequilibrium

CerebellumCerebellum Has three regions: Outer cortical gray matter, Has three regions: Outer cortical gray matter,

Inner white matter (arbor vitae) and Deep Inner white matter (arbor vitae) and Deep cerebellar nuclei.cerebellar nuclei.

Cerebellar cortical nuclei function to smooth Cerebellar cortical nuclei function to smooth body movements.body movements.

White matter contains tracts that carry White matter contains tracts that carry information to information to

and from cerebral cortex.and from cerebral cortex.

Deeper nuclei relay instructions to other areas Deeper nuclei relay instructions to other areas of brain from cerebellar cortex to refine body of brain from cerebellar cortex to refine body movements.movements.

CerebellumCerebellum Cerebellar cortex receives 3 forms of Cerebellar cortex receives 3 forms of

information :information : 1). Equilibrium, 2). Position of muscles in limbs, 1). Equilibrium, 2). Position of muscles in limbs,

neck and trunk and 3). Info from cerebral cortex.neck and trunk and 3). Info from cerebral cortex.

Cerebellar peduncles are fibers tracts that Cerebellar peduncles are fibers tracts that connect cerebellum with different parts of brain.connect cerebellum with different parts of brain.

Unlike cerebral motor outflow which is Unlike cerebral motor outflow which is contralateral, cerebellar outflow is ipsilateral contralateral, cerebellar outflow is ipsilateral (same side).(same side).

CerebellumCerebellum

CerebellumCerebellum

Cranial NervesCranial Nerves Twelve pairs of cranial nerves arise from Twelve pairs of cranial nerves arise from

nuclei in brain and migrate out of cranium nuclei in brain and migrate out of cranium to innervate peripheral organs.to innervate peripheral organs.

First 2 pairs arise from forebrain, the First 2 pairs arise from forebrain, the remainder come from brainstem nucleiremainder come from brainstem nuclei

They are numbered in Roman numerals I They are numbered in Roman numerals I thru XII.thru XII.

All cranial nerves except for X innervate All cranial nerves except for X innervate head and neck.head and neck.

Cranial nerve X (Vagus) innervates head, Cranial nerve X (Vagus) innervates head, neck, thorax and abdomen.neck, thorax and abdomen.

Cranial NervesCranial NervesII Olfactory nerve (S) Olfactory nerve (S) VIIVII Facial (B) Facial (B)

IIII Optic nerve (S) Optic nerve (S) VIIIVIII Vestibulochochlear Vestibulochochlear (S)(S)

IIIIII Occulomotor (M) Occulomotor (M) IXIX Glossopharyngeal (B)Glossopharyngeal (B)

IVIV Trochlear (M) Trochlear (M) XX Vagus (B) Vagus (B)

VV Trigeminal (B) Trigeminal (B) XIXI Accessory (M) Accessory (M)

VIVI Abducens (M) Abducens (M) XIIXII Hypoglossal (M) Hypoglossal (M)

Oh, Oh, Oh To Touch And Feel Velvet, Good Oh, Oh, Oh To Touch And Feel Velvet, Good Vibrations And Harmony.Vibrations And Harmony.

I. Olfactory nerves (S)I. Olfactory nerves (S) Strictly sensory for smell.Strictly sensory for smell. Nerve fibers are in cribriform plate of Nerve fibers are in cribriform plate of

ethmoid boneethmoid bone

I Olfactory nerve fibersI Olfactory nerve fibers

II. Optic nerves (S)II. Optic nerves (S) Strictly sensory for visionStrictly sensory for vision Enters cranium via optic foramen Enters cranium via optic foramen

anterior to pituitary gland in sella anterior to pituitary gland in sella turcica.turcica.

II Optic nervesII Optic nerves

III. Occulomotor nerves III. Occulomotor nerves (M)(M)

Primarily motor nerve to extrinsic eye Primarily motor nerve to extrinsic eye muscles (inferior oblique, sup., inf. and muscles (inferior oblique, sup., inf. and medial rectus muscles)medial rectus muscles)

III Occulomotor to eye III Occulomotor to eye musclesmuscles

IV. Trochlear nerves (M)IV. Trochlear nerves (M) Primarily motor to superior oblique eye Primarily motor to superior oblique eye

musclesmuscles

IV Trochlear nerve to sup. IV Trochlear nerve to sup. obliqueoblique

V. Trigeminal nerves (B)V. Trigeminal nerves (B) Mixed nerve with 3 divisions to face; Mixed nerve with 3 divisions to face;

largest cranial nerve.largest cranial nerve.

V Trigeminal to face and V Trigeminal to face and jawjaw

VI. Abducens nerves (M)VI. Abducens nerves (M) Primarily motor to lateral rectus muscle Primarily motor to lateral rectus muscle

of eyeof eye

VI Abducens to lateral VI Abducens to lateral rectusrectus

VII. Facial nerves (B)VII. Facial nerves (B) Mixed nerve with 5 branches to neck and Mixed nerve with 5 branches to neck and

face.face.

VII Facial nerve distribution – VII Facial nerve distribution – five branches five branches to face & neckto face & neck

VIII. Vestibulocochlear VIII. Vestibulocochlear nerves (S)nerves (S)

Purely sensory for hearing and Purely sensory for hearing and equilibriumequilibrium

VIII Vestibulocochlear to VIII Vestibulocochlear to inner earinner ear

IX. Glossopharyngeal IX. Glossopharyngeal nerves (B)nerves (B)

Mixed nerve to pharynx, post. tongue, Mixed nerve to pharynx, post. tongue, parotid glandsparotid glands

IX Glossopharyngeal to tongue and IX Glossopharyngeal to tongue and salivary glandssalivary glands

X. Vagus nerves (B)X. Vagus nerves (B)

Mixed nerve extends to thoracic and Mixed nerve extends to thoracic and abdominal cavities; parasympathetic to abdominal cavities; parasympathetic to heart, lungs and abdomenheart, lungs and abdomen

XI. Accessory nerves (M)XI. Accessory nerves (M) Motor nerves to larynx, pharynx and Motor nerves to larynx, pharynx and

neck muscles for swallowingneck muscles for swallowing

XI Accessory to neck XI Accessory to neck musclesmuscles

XII. Hypoglossal nerves XII. Hypoglossal nerves (M)(M)

Motor to muscles of tongue Motor to muscles of tongue

XII Hypoglossal to tongue XII Hypoglossal to tongue musclesmuscles